Strip configuration for capacitors

ABSTRACT

The present invention relates to a configuration which is an integral part of the anode structure of an electrolytic capacitor. A strip of film-forming metal includes at least one appendage which has formed therein a depression which serves as the retaining means for a bonded mass of film-forming metal. The appendage also includes a reduced neck portion. The appendage and the mass of film-forming metal have an oxide layer, a semiconductor layer and a conductive layer formed thereover. Terminal means includes one extremity having a bent end portion connected to the reduced neck portion and includes another extremity having a substantially flatten end portion connected to the conductive layer carried by the bonded mass of film-forming metal.

1 51 May 30, 1972 [54] STRIP CONFIGURATION FOR CAPACITORS Gerhai-t P.Klein, Manchester, Mass.

P. R. Mallory 8: Co., Inc., Indianapolis, Ind.

[22] Filed: June 1,1970

[21] Appl.No.: 54,066

[72] Inventor:

[73] Assignee:

Related U.S. Application Data [62] Division of Ser. No. 722,702, Apr.19, 1968, Pat. No.

2,743,400 4/ l 956 3,325,699 1/1967 Hellicar. ...3 1 7/230 3,403,3039/1968 Klein ..3 17/230 Primary Examiner-James D. Kallam AttorneyRichardH, Childress and Robert F. Meyer [5 7] ABSTRACT The present inventionrelates to a configuration which is an integral part of the anodestructure of an electrolytic capacitor. A strip of film-forming metalincludes at least one appendage which has formed therein a depressionwhich serves as the retaining means for a bonded mass of film-formingmetal. The appendage also includes a reduced neck portion. The appendageand the mass of film-forming metal have an oxide layer, a semiconductorlayer and a conductive layer formed thereover. Terminal means includesone extremity having a bent end portion connected to the reduced neckportion and includes another extremity having a substantially flattenend portion connected to the conductive layer carried by the bonded massof film-forming metal.

10 Claims, 6 Drawing Figures Bujan ..3l7/23O Patented May 30, 19723,667,002

INVENTOR GERHART P. KLEIN ATTORNEY STRIP CONFIGURATION FOR CAPACITORSThis is a division of application Ser. No. 722,702, filed Apr. 19, 1968,now U.S. Pat. No. 3,530,342.

Solid electrolyte capacitors may be manufactured using any one ofseveral techniques. For example, a film-forming metal powder selectedfrom the group consisting of tantalum, niobium, hafnium, zirconium,aluminum and titanium may be pressed into the desired configurationhaving the desired density and then sintered so as to provide a porousanode slug or pellet. The anode slug may be prepared using a mixture ofthe film-forming metal powder and a binder such as stearic acid or thelike. The binder is used to hold the compressed particles together untilsintering of the particles has been initiated. During sintering of thecompact, the stearic acid is evaporated without leaving harmfulimpurities on or in the compact. Sintering bonds the individualfilm-forming metal particles together so as to form a slug having amyraid of intercommu nicating voids. An oxide film may be formed on thefilm-forming metal using any known electroformation method. The

oxide film serves as the dielectric for the electrolytic capacitor. Inthe case of a tantalum slug, the oxide film is tantalum oxide (T21 O Theoxide film coated slu gmay be dipped into a solution of a material suchas manganeous nitrate which may be pyrolytically converted toasemiconductive material such as manganese dioxide which substantiallyoverlies the dielectric oxide film. The-manganese dioxide layerfunctions as the counter electrode (cathode) of the capacitor. The stepof forming the oxide film dielectric layer and/or the steps of formingthe manganese dioxide semiconductive layer on the slug may be repeatedas many times as is necessary to achieve a capacitor having the desiredelectrical characteristics. The slug may be dipped into a solutioncontaining a suitable contact material such as a colloidal dispersion ofgraphite in water or the like and may be suitably cured by heating at anelevated temperature in an oven. Thelast mentioned step is performed inorder to provide a graphite layer over the semiconductor layer on atleast the end of the slug removed from the anode riser. Silver paint"may be applied over the graphite layer and suitably cured by heating atan elevated temperature in an oven. Thereafter, the slug may bedippedinto molten solder and the molten solder allowed to cooLThe slugis placed in a suitable container or housinggenerally having an. openend and aclosed end. The end of the slug coated with solder may besuitable attached to the casing by any suitable means such as solder andthe like. The open end of the container may be closed with a suitableend seal such as an hermetic glass-tometal seal, gasket seal or thelike. 7

The coated. slug may beencapsulated in a plastic material by generallyaccepted plastic encapsulation processing techniques such as by dipping,transfer molding, injection molding and the like.

It is known that solid electrolyte capacitors may be fabricated using asubstantially continuous fabricating process. The substantiallycontinuous process used to fabricate the capacitors may be any one ofseveral different processes. The continuous fabrication process referredto in the said application is generally known as the powder on foilprocess. The powder on foil process was conceived and developed tosubstantially eliminate handling problems experienced during thefabrication of small, solid electrolyte capacitors. The powder on foilprocess described in the said application significantly reduces thehandling required during fabrication of the'capacitors when compared tothe handling required during the fabrication of solid electrolytecapacitors using pressed anode slugs. Also, it was found that theelimination of the binder used to hold the mass of metal together priorto sintering and the elimination of the pressing step improved thequality of the solid electrolyte capacitor.

The powder on foil process consists essentially of forming asubstantially continuous foil strip of film-forming metal into thedesired, configuration, depositing a moistened mass of film-formingmetallic powder on the foil strip and sintering the moistened mass ofmetallic powder in situ to form a porous pellet connected to-the foilstrip. The pellet, of course, is the anode of the capacitor. The pelletis further processed so as to be provided with a cathode terminalthereby completing the capacitor unit. It should be seen that the powderon foil" technique substantially reduces the amount of handling requiredduring fabrication of the capacitor, substantially eliminatescontamination which may occur during handling and substantiallyminimizes the possibility of structural damage occurring to thecapacitor during fabrication by eliminating the steps of adding bindersto the powder prior to sintering and pressing of the mass of powder.

The use of a moistened mass of film-forming metal powder has severaladvantages, among which is that the moistened powder flows drop .wisefrom a suitable dispenser thereby facilitating the dispensing of themoistened mass'of powder in controlled amounts. Another advantage of theabove-mentioned process is that the dispensed moistened mass offilmforming metal powder has a significantly reduced volume whencompared to the volume of the dry film-forming metal powder, therebyproviding a green compact having a suffciently high density withoutsubjecting the mass of film-forming metal powder to a compacting step.

It was found, however, that if the portion of the strip offilmformingmetal foil, that is, the appendage; carrying the mass of powder isdisplaced with respect to the remaining portion of the strip of metaldamage to the capacitor may result. Also, alignment of the terminalmeans with respect to the appendage, at times, proved difficult.

Therefore, it is an object of the present invention to provide afilm-forming metal foil strip means including at least one appendage foruse in electrolyte capacitor which overcomes the above-mentionedproblems.

A further object of the present invention is to provide a method forfabricating miniature capacitor components using automated techniques.

Another object of the present invention is to provide a hairpin terminalmeans for use with a film-forming metal foil strip having at least oneappendage which is carried by the foil strip.

Yet another object of the present invention is to provide a foil striphaving at least one appendage and having means for providing alignmentof terminal means with the cooperatively associated appendage.

A further object of the present invention is to provide, during themanufacture of an electrolyte capacitor, foil strip means which carrythe terminal lead means of the capacitor and wherein the terminalleadmeans serve in assisting the positioning of the capacitor within amold cavity prior to encapsulation of the capacitor.

Another object of the present invention is to provide a capacitorutilizing hairpin terminal means which substantially preventsdisplacement of the capacitor within the confines of a mold cavityduring the molding of a housing about the capacitor thereby providing amolded housing having a substantially uniform thickness about thecapacitor.

Yet another object of the present invention is to provide cup-shapedmeans of film-forming metal foil strip'carrying a bonded mass offilm-forming metal powder having a myriad of intercommunicating voidswhich includes a reduced neck portion and means to support a selectedregion of the neck portion thereby substantially preventing deformationof the strengthened region of the reduced neck portion with respect tocup-shaped means during processing at various work stations which maylead to damage of the completed capacitor.

A further object of the present invention is to provide a film-formingmetal foil strip means which includes at least one aperture having asubstantially continuous side wall at substantially a right angletherewith so as to increase the mechanical strength of the aperturewithout a corresponding increase in the physical thickness of the foilstrip means.

Another object of the present invention is to provide a filmforrningmetal foil strip having a plurality of appendages which is automaticallyindexed under the desired work station.

Still another object of the present invention is to provide a foil stripconfiguration of film-forming metal for use in the fabrication of anelectrolytic capacitor which includes a specially designed neck portionwhich reduces damage thereto during fabrication of the capacitor.

Yet another object of the present invention is to provide a foil stripof film-forming metal including cup-like means which are substantiallyrectangular-shaped so as to make most efiicient use of a rectangularhousing used to encapsulate the capacitor.

A further object of the present invention is to provide a foil strip offilm-forming metal including cup-like means connected to the foil stripby a reduced neck portion for an electrolytic capacitor wherein thepositive lead therefore is bent over and welded to the narrow part ofthe neck configuration associated with the strip configuration.

With the aforementioned objects enumerated, other objects relevant tothe present invention will be apparent to those persons possessingordinary skill in the art. Other objects of the present invention willappear in the following description, appended claims and appendeddrawings. The invention resides in the novel constructi6n, combination,arrangement and cooperation of elements as hereinafter described and,more particularly, as defined in the appended claims.

The appended drawings illustrate embodiments of the present inventionconstructed to function in an advantageous mode devised for thepractical application of the basic principles in the hereinafterdescribed invention.

In the drawings:

FIG. 1 is an enlarged partial top view of a foil strip means of filmforming metal including integral appendages illustrating the position ofhairpin terminal means with respect to the cooperatively associatedappendage and the retention and alignment thereof with respect to theappendage by means carried by the foil strip. I

FIG.- 2 is a side view of the foil strip and appendage taken across thelines 22 of FIG. 1, illustrating the reinforced section of an apertureand means used to support the neck portion of the appendage;

FIG. 3 is a cross-sectional view taken across the lines 33 of FIG. 1,illustrating means used to position and retain said hairpin terminalmeans during processing of the foil strip;

FIG. 4 illustrates said hairpin terminal means having a bent over endconnected to the reduced neck portion of the appendage and a flatten endconnected to the contact layer carried by the cup-shaped member of theappendage;

FIG. 5 is a partial top view of the appendage illustrating reinforcingrib means carried by the reduced neck portion to thereby strengthen thereduced neck portion; and

FIG. 6 is a cross-sectional view of the capacitor device illustratingencapsulation of the capacitor device.

Generally, speaking, the present invention relates to the means andmethods of fabricating miniature capacitors. A cup-shaped means includesa depression for retaining bonded mass a filmforming metal particles. Areduced neck portion is integrally connected to the cup-shaped means.Terminal means including at least one bent over anode lead is attachedto the reduced neck portion. The region of attachment of the anode leadto the reduced neck portion is spaced from the cup-shaped means.

Referring now to the enlarged top view illustrated in FIG. 1 of thedrawings, strip 10 of the film-forming metal foil includes base 11 and aplurality of appendages 12. The film-forming metal used to fabricate thestrip and appendages is selected from the group consisting of tantalum,aluminum, niobium, hafnium, zirconium, titanium and the like. The base11 of film-forming metal is preferably provided with a series ofsubstantially equally spaced pilot apertures or perforations 13 whichpermit indexing of the strip material to and through the individual workstations as well as providing a convenient means by which thestripmaterial may be advanced before and after each operational cycleperformed on the cup-shaped members 18 of the appendage at the workstations. The apertures are illustrated as being substantiallyrectangular in shape. However, the shape and size of the aperturesdepend on, among other things, the shape and size of the sprocket meansused to drive the strip material. Round apertures and rectangularapertures with or without an eyelet or side walls 15 and 15 may be used.Rectangular apertures with eyelets or side walls are preferred in orderto give the strip additional strength which enables the foil strip to bewound on appropriate reel type devices and facilitate accurate indexingof the foil strip and the appendages to and through the stations atwhich work is to be performed on the foil strip and appendage.

The strip material 10 may be provided with a plurality of spaced,transversely aligned longitudinal extending means 14 disposedsubstantially intermediate successive pilot apertures 13. The extendingmeans each include an angulated side 17 and 17' at each extremitythereof. Between each of the sides 15 and 15' of the aperture 13 and theprojecting means 14 there is formed a receiving channel for the hairpinterminal means 16. It should be seen that the sides of 15 and 15' of theaperture and the angulated sides 17 and 17 of the extending means 14cooperate to position and retain the hairpin terminal means 16. Theextending means accurately positions and substantially fixedly retainsthe hairpin means with respect to the cooperatively associatedcup-shaped means. The extending means are illustrated as tabs formedfrom the foil strip and bent at a substantially right angle with respectto the foil strip and thereby serve the function of assisting in thepositioning and in the rotation of the hairpin lead in its desiredlocation with respect to the cooperatively associated cup-shaped means.

The shape of the film-forming metal foil strip and the appendageintegrally formed therewith is, in part, determined by the shape of thehousing used to encapsulate the capacitor. In the embodiment shown in hefiguresv of the drawings, the rectangular-shape cups 18 may be pressedinto the film-forming metal foil by using a suitable die whichsimultaneously cuts the foil into suitable size, forms the desiredconfiguration of the cup-shaped means, and forms the unit outline. Forillustrative purposes only and not for purposes of limiting the presentinvention, two mil thick foil is cut into appendages having a reducedneck portion and a rectangular cup-shaped means. The rectangularcup-shaped means has a length of about 150 mils, a width of about I20mils and a depth of about 10 mils. The center distance betweenindividual cups is about 200 mils.

The cup-shaped portion 18 is usedto carry the mass of bondedfilm-forming metal particles. The rectangular-shaped cup appears to makemost efficient use of the available space in a rectangular type ofhousing. The foil carrying the mass of metal powder is cup-shaped for itis believed that it would otherwise be difficult to retain droplets ofmoistened metal powder within a selected area. The drops of moistenedmetal should be retained within a selected area so that the portion ofthe strip containing each of the droplets may separate from each otheraccurately and conveniently and so that each resultant capacitor hassubstantially the same capacitance rating. Further, the moistened powdertends to run over the edges of a flat appendage if the appendage doesnot contain an area thereof which acts as a confining means for themoistened mass-of film-forming metal powder.

Each appendage also includes a reduced neck portion 19 which connectsthe cup-shaped means to the base of the foil strip. With the aboverecited dimensions of the rectangular cup-shaped means in mind, thereduced neck portion is gradually reduced in width from about mils toabout 40 mils a distance of about 40 mils from he cup-shaped means. Thetotal length of the reduced neck portion is about mils. It should beseen that the gradual reduction of the neck portion extends abouttwo-sevenths of the total length of the neck portion and that the neckportion is reduced to about onethird of is width at the rectangularshaped cup.

The neck portion of the device is designed in such a manner so that anydisplacement of the appendage or appendages with respect to the base ofthe metal foil strip does not result in a defective capacitor. Thedanger of displacement of the appendage with respect to the main body ofthe foil strip is particularlyacute during attachment of the terminalmeans 16 to the appendage and in the molding steps. The foil is shapedin such a way that the neck portion immediately adjacent to thecupshaped mean is stronger than the neck portion adjacent to the base ofthe foil strip. Using thedimensions given as illustrated in the presentinvention, the area of flexing is encouraged to take place 40 milsremoved from the cup-shaped means.

If theend of the terminal meansis connected too close to the cup, theheat associated with connecting the end of the lead to the neck portionmay be sufficient to cause the oxide film to be partially ortotallydestroyed. Therefore, the terminal means has an end connected tothe narrow portion of the neck far enough from the neck to preventdamage to the capacitor body. g

The hairpin terminal mean s' l6 includes one extremity 20 whichisflattened so asto provide intimatecontact with the contact layer(n'ot'shown') formed on the bonded film-forming metal mass 26 disposedin the cup 18 of the appendage 12. .The hairpin terminal meanslincludeselongated sections 21 and 2l' which engage the angulated sides '17 and1? respectively of the extending means 14 and engages with the sidewalls 15 and 15" respectively of the rectangular aperture 13. Forexample, the elongated section21" of the hairpin terminal means engageswith a side wall 15' of the aperture 12 and an angulated side 17."ofextending means 14. It should be seen that .the hairpin means isrestrained from horizontal and vertical displacement by the cooperativeassociation existing between the angulated side 17 of'the extendingmeans 14, and side wall 15"of aperture 13, 'and'the flat portion 22 ofthe foilstrip." j i The hairpin terminal means also includessubstantially U- shaped segment -13'located approximately mid-waybetween 'the'terininal ends. The hairpin means may include a bent overextremity 23 which is welded to the reduced neck portion 19 of thecup-shaped means at 24. The extremity 23 of the hairpin means may besubstantially straight if the indexing apertures l3 and'the extendingmeans 14 are displaced slightly from their positions illustrated inFIGS. 1 and 3.

- Referring now to FIG. 2 of the drawing, it should be seen that theside walls 15 and I5"of aperture 12 support the filmforming'inetalbase11 during processing through the various work stations. Theextendingmeans 14 and the side walls 15 and 15'- of the aperture 12 are used tomaintain the film-fenning metal foil on a plane substantially parallelwith guide means 25 positioned below'the film-forming metal foil strip.

FIG. 4 shows the appendage consisting of the cup-shaped means-and thereduced neck portion removed from the filmforming metal foil base 11..The, cup-shaped means and reduced neck portion may be removed from thefoil base by any suitable cutting means such as a knife cutter (notshown) or. the like. FIG. 4 also shows that the bent end portion of thehairpin terminal mean is welded to the reduced neck portion of thecup-shaped means at a point substantially removed from the rectangularcup-shaped means so that heat from the welding strip does not. degradethe oxide film on the cupshaped means. The flattened end of the hairpinterminal means is connected to the contact layer formed on thefilmforming metal by any suitable means such as solder or the like.

Rib means shown in FIG. 5 maybe embossed in the neck portion of theappendage to further strengthen the are of the reduced neck portion ofthe appendage so that flexing thereof, if any, occurs in an area removedfrom the cup-shaped portion of the foilmeans. I

FIG. 6 shows capacitor body encapsulated in a suitable resilient orelastomeric housing means 31. The capacitor body includes the cup'shapedmeans, the reduced neck portion, the hairpinterminai means, adielec'tricoxide layer, a semiconductor layer and a contact layer. Thehousing means is molded directly to the capacitor body by any suitablemolding technique such as injection molding or transfer molding. Thematerial of the housing may be selected from any suitable thermosettingor thermoplastic material such as for example,

silicone rubber, epoxy, polycarbonate, phenolic or .the like. Thehairpin terminal means of FIG. 4 is used for several functions otherthan the functions enumeratedvabove. An additional function of theterminal means is accurately position the capacitor body within the moldmeans'(not shown). In' addition, the terminal means is used to provideadded strength to the capacitor body so that it is not displaced withinthe molded cavity by the introduction of' molten material into thecavity. After the capacitor has been removed from the hold, the hairpinterminal lead is severed insuch a manner so as to form'two separate anddistinct leads so as to provide an anode lead and a cathode lead. Thelead connected to the reduced neck portion is the anode lead and thelead connected to the contact layer is the cathode lead. R

The present invention is not'intended to be limited to the disclosureherein and changes and modifications may be made in the disclosure bythose skilled in the art without departing from the spirit and scope ofthe novel concepts of this invention. Such modifications and variationsare considered to be within the purview and scope of this invention andthe appended claims.

. Having thus described my invention, Iclaim:

1. In a capacitor, having amass of bonded film-forming metal powderswith a myriad of intercommunicating voids, a metal oxide layer formedover the surface of said metal powders, a semiconductor electrolytelayer'formed over the said metal oxide layer, a contact layer formedover the electrolyte layer, and a housing encapsulating said capacitor;the improvement comprising; a cup-shaped means including a depressioncontaining said mass of bonded film-forming metal powders, saidmassbeing integrally bonded to said cup-shaped means, a neck portionintegrally connected to and projecting from the cup-shaped means, andterminal means including at least one anode lead attached to said neckportion at a location spaced from said cup-shaped means, and saidterminal means including at least one cathode lead attached to saidcontact layer. v

2. In the capacitor of claim 1, wherein said anode lead in cludes a bentover portion attached to said neck portion.

3. In the capacitor of claim 1, further including means. forstrengthening said neck portion between said cup-shaped means and thearea where said anode lead means is attached to said reduced neckportion.

4. In the capacitor of claim 3, wherein said means for strengtheningsaid neck portion is a gradual reduction for the width of said neckportion starting at said cup-shaped means.

5. In the capacitor of claim 4, wherein the gradual reduction of saidneck portion is confined to about the initial twosevenths of the entirelength of said neck portion.

6. In the capacitor of claim 4, wherein said'means for strengtheningsaid neck portion further includes rib means which extends the length ofsaid gradual reduction of said width of said neck portion.

7. In the capacitor of claim 1, wherein the cup-shaped 'means issubstantially rectangular-shaped.

1. In a capacitor, having a mass of bonded film-forming metal powderswith a myriad of intercommunicating voids, a metal oxide layer formedover the surface of said metal powders, a semiconductor electrolytelayer formed over the said metal oxide layer, a contact layer formedover the electrolyte layer, and a housing encapsulating said capacitor;the improvement comprising; a cup-shaped means including a depressioncontaining said mass of bonded film-forming metal powders, said massbeing integrally bonded to said cup-shaped means, a neck portionintegrally connected to and projecting from the cup-shaped means, andterminal means including at least one anode lead attached to said neckportion at a location spaced from said cup-shaped means, and saidterminal means including at least one cathode lead attached to saidcontact layer.
 2. In the capacitor of claim 1, wherein said anode leadincludes a bent over portion attached to said neck portion.
 3. In thecapacitor of claim 1, further including means for strengthening saidneck portion between said cup-shaped means and the area where said anodelead means is attached to said reduced neck portion.
 4. In the capacitorof claim 3, wherein said means for strengthening said neck portion is agradual reduction for the width of said neck portion starting at saidcup-shaped means.
 5. In the capacitor of claim 4, wherein the gradualreduction of said neck portion is confined to about the initialtwo-sevenths of the entire length of said neck portion.
 6. In thecapacitor of claim 4, wherein said means for strengthening said neckportion further includes rib means which extends the length of saidgradual reduction of said width of said neck portion.
 7. In thecapacitor of claim 1, wherein the cup-shaped means is substantiallyrectangular-shaped.
 8. In the capacitor of claim 7, wherein the anodeattachment is along substantially the entire longitudinal length of oneside of said rectangular-shaped cup means.
 9. In the capacitor of claim7, wherein said film-forming metal of said cup means and said mass ofbonded film-forming metal particles is the same.
 10. In the capacitor ofclaim 9, wherein film-forming metal is selected from the groupconsisting of tantalum, aluminum, titanium, niobium, hafnium andzirconium.